Non-Hodgkin's lymphomas (NHLs) represent a heterogeneous group of malignancies arising from the lymphoid system. They represent the malignant counterpart of different steps of B-lymphocyte differentiation. Similar to other types of cancer, they are the result of a multistep accumulation of genetic aberrations that induce a selective growth advantage of the malignant clone [Nogai H, Dorken B, Lenz G. Pathogenesis of non-Hodgkin's lymphoma. J. Clin. Oncol. 2011; 29(14), 1803-1811]. The World Health Organization classifies NHLs in three main groups: a) mature B cell neoplasms, b) mature T cell and natural killer (NK) cell neoplasms and c) immunodeficiency-associated lymphoproliferative disorders. Among the mature B cell neoplasms, chronic lymphocytic leukemia, mantle cell lymphoma, follicular lymphoma and diffuse large B cell lymphoma represent the four most relevant ones.
Chronic lymphocytic leukemia (CLL) is one of the most frequent tumors in Western countries. CLL represents 35% of all leukemias with an incidence of 3-7 per 100.000 habitants and reaches 12-15/100.000 in people over 60 years. The disease is clinically heterogeneous; some patients have a long clinical evolution with a stable disease, whereas others follow a progressive course with a median survival of 5-8 years. This heterogeneity is due to the existence of two major molecular groups, characterized respectively by the presence or absence of somatic mutations in the immunoglobulin genes. Different genetic alterations have been identified associated with particular clinical presentations and evolution. There is also evidence of genetic predisposition, but the initiating genetic alterations are largely unknown in both sporadic and inherited cases, and the somatic genetic basis of CLL remains largely unknown [Zenz T, Mertens D, Kuppers R, et al. From pathogenesis to treatment of chronic lymphocytic leukaemia. Nat. Rev. Cancer 2010; 10(1), 37-50]. Current treatments for the disease include chemotherapy, such as treatment with alkylating agents (chlorambucil, cyclophosphamide, bendamustine), purine analogs (fludarabine) and immunotherapeutic agents (rituximab and alemtuzumab), or the combination of immuno- and chemotherapy (the gold standard for CLL treatment is now fludarabine, cyclophosphamide and rituximab). However, none of these treatments are curative.
Mantle cell lymphoma (MCL) accounts for 5% to 10% of all lymphoma cases in adults. The overall incidence of MCL per 100.000 habitants is 0.55, increasing with age: 0.07 in patients aged <50 years, 2.97 in patients aged 70 to 79 years, and 2.78 in those aged > or =80 years. MCL is a B-cell neoplasia genetically characterized by the t(11;14)(q13;q32) translocation and the overexpression of its target gene cyclin D1. This tumor is considered one of the most aggressive lymphoid neoplasias and most patients follow a relative rapid evolution with limited responses to the current therapeutic strategies [Jares P, Colomer D, Campo E. Molecular pathogenesis of mantle cell lymphoma. J. Clin. Invest. 2012, 1; 122(10), 3416-23]. The current therapeutic strategies for the treatment of MCL are based on the use of combination chemotherapy with rituximab or more recently the use of bendamustine plus rituximab. In the last six years, two new drugs for relapsed or refractory MCL have been approved: the proteasome inhibitor bortezomib (approved by the US FDA) and the mTOR inhibitor temsirolimus (approved by the European Medicines Agency). Patients afflicted with MCL suffer from frequent relapses and they progressively develop resistance to treatment, emphasizing the need for new approaches. Currently, transplantation of hematopoietic progenitors (THP) is the only curative regimen, but it is not doable in the commonly aged patients affected from this lymphoma.
Follicular lymphoma (FL) is the most frequent low-grade NHL and accounts for approximately 20% of all malignant lymphomas with approximately 3 to 5 per 100.000 habitants and increases with age, with the median age at diagnosis being 60 years. The clinical course of FL can be highly variable, with overall survival rates ranging from only a few to more than 20 years. FL is derived from a germinal center B cell and is characterized by the presence of t(14;18)(q32;q21) translocation that juxtaposes the BCL2 gene and the IGH locus, leading to the overexpression of the antiapoptotic protein BCL2 [Kridel R, Sehn L H, Gascoyne R D. Pathogenesis of follicular lymphoma. J. Clin. Invest. 2012, 122(10), 3424-3431]. Most of FL patients show complete or partial responses with immunotherapy treatment. However, relapses are warranted in most of the cases making this disease incurable.
Diffuse large B-cell non-Hodgkin's lymphoma (DLBCL) constitutes 30%-58% of non-Hodgkin's lymphoma series representing the most frequent lymphoma. The crude incidence in the European Union is 3-4/100,000 per year and increases with age from 0.3/100,000/year (35-39 years) to 26.6/100,000/year (80-84 years) [H. Tilly, M. Dreyling (On behalf of the ESMO Guidelines Working Group). Diffuse large B-cell non-Hodgkin's lymphoma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann. Oncol. 2010; 21(suppl 5): v172-v174].
Treatment strategies of FL and DLBCL should be stratified according to age and the Follicular Lymphoma International Prognosis Index (FLIPI) or International Prognosis Index (IPI) that allows the feasibility of dose-intensified approaches based on patient's health report. Most of the treatments are based on the use of combination chemotherapy (mainly cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP)) combined with rituximab. Lately, maintenance therapy with rituximab seems to delay the common relapses seen in these lymphomas.
The literature has reported that the most upstream tyrosine kinases LYN, SYK (spleen tyrosine kinase), and BTK (Bruton's tyrosine kinase) in the B-Cell Receptor (BCR) pathway are involved in NHLs, in particular in mature B cell neoplasms.
Dasatinib is an oral multikinase inhibitor targeting SRC and ABL kinases that is approved for treatment of chronic myeloid leukemia. Dasatinib has also been shown to inhibit LYN and BTK at low nanomolar concentrations. In vitro, dasatinib induces variable degrees of apoptosis in CLL cells [McCaig A M, Cosimo E, Leach M T, Michie A M. Dasatinib inhibits B cell receptor signalling in chronic lymphocytic leukaemia but novel combination approaches are required to overcome additional pro-survival microenvironmental signals. Br. J. Haematol. 2011, 153(2), 199-211; and López-Guerra M, Xargay-Torrent S, Péréz-Galán P, Saborit-Villarroya I, Rosich L, Villamor N, Aymerich M, Roué G, Campo E, Montserrat E, Colomer D. Sorafenib targets BCR kinases and blocks migratory and microenvironmental survival signals in CLL cells. Leukemia. 2012, 2 6(6), 1429-32]. Dasatinib as a single agent has activity in relapsed and refractory CLL. (Amrien et al, Amrein P C, Attar E C, Takvorian T, et al. Phase II study of dasatinib in relapsed or refractory chronic lymphocytic leukemia. Clin Cancer Res 2011; 17:2977-86; Al-Ameri A M, Badoux X, Ferrajoli A, et al. Phase II study of dasatinib in patients with relapsed chronic lymphocytic leukemia. Blood 2010; 116:4488). Dasatinib has been evaluated in CLL in combination with other drugs including rituximab, lenalidomide and bendamustine. In summary, it seems that dasatinib is an effective part of CLL treatment, particularly in the reduction of nodular tumor masses, but seems to have week efficacy on peripheral lymphocytes (Robak T, Robak E. Tyrosine kinase inhibitors as potential drugs for B-cell lymphoid malignancies and autoimmune disorders. Expert Opin Investig Drugs. 2012 July; 21(7):921-47).
The first clinical trial of a SYK inhibitor in a non-Hodgkin's lymphoma used fostamatinib in a phase 1/2 study in patients with relapsed/refractory non-Hodgkin's lymphoma and CLL [Friedberg J W, Sharman J, Sweetenham J, et al. Inhibition of Syk with fostamatinib disodium has significant clinical activity in non-Hodgkin's lymphoma and chronic lymphocytic leukemia. Blood 2010; 115(13):2578-2585]. The dose-limiting toxicity was a combination of diarrhea, neutropenia, and thrombocytopenia. In the phase 2 portion of the trial, the most common adverse events were reversible cytopenias, fatigue, diarrhea, and hypertension. Of 11 patients with CLL, 6 (55%) achieved a partial response (PR). The response rate in CLL was the highest, ahead of DLBCL (22%), MCL (11%), and FL (10%). Moreover, analysis of CLL patient material enrolled in this phase 1/2 study was used to evaluate the effects of fostamatinib on CLL cells in vivo after one cycle of treatment. This analysis demonstrated that Fostamatinib inhibits BCR signaling, cellular activation and tumor proliferation in vivo, in patients with relapsed and refractory chronic lymphocytic leukemia (S E M Herman et al Leukemia epub 1 Mar. 2013).
Newer more potent and more specific SYK inhibitors are in development [Hoellenriegel J, Coffey G P, Sinha U, et al. Selective, novel spleen tyrosine kinase (Syk) inhibitors suppress chronic lymphocytic leukemia B-cell activation and migration. Leukemia 2012, 26(7):1576-1583].
Ibrutinib is a BTK inhibitor, whose initial phase 1 dose escalation study reported responses in 60% of patients with various B-cell malignancies. In the 14 patients with CLL, the overall response (OR) was 79%, including 2 complete responses (CR). [Advani R H, Sharman J P, Smith S M, et al. The BTK inhibitor PCI-32765 is highly active and well tolerated in patients with relapsed/refractory B-cell malignancies: final results from a Phase I study. Ann. Oncol. 2011. Abstract 153]. A phase 1b/2 study of ibrutinib in CLL enrolled 2 cohorts: treatment-naive patients >65 years and relapsed/refractory patients. In the latter cohort, best responses were PR in 66% and complete responses in 1 of 61 patients studied, with no difference between dose levels [O'Brien S, Burger J A, Blum K A, et al. The Bruton's tyrosine kinase (BTK) inhibitor PCI-32765 induces durable responses in relapsed or refractory (R/R) chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL): follow-up of a Phase Ib/II study. Blood (ASH Annual Meeting Abstracts) 2011, 118(21), 983]. Ibrutinib was well tolerated, and the most common side effects were diarrhea, nausea, fatigue, echymosis, upper respiratory tract infections, muscle spasms, arthralgia, peripheral edema, and pyrexia. The follow up of this study in 2012 further confirmed that ibrutinib was active in the treatment of naive patients (overall response (OR) of 71%, with complete response (CR) of 10% and partial response (PR) of 61%), relapsed/refractory patients (OR 67% with CR 3%, PR 64%), and high risk patients (OR 50% with CR 0%, PR 50%), with an estimated overall survival (OS) of 22 month in 96% of treated naive patients and 76% of relapsed/refractory and high risk patients (Byrd J, Blood 2012 120:21 Abstract 189)
In a phase 1 clinical trial in relapsed follicular lymphoma, ibrutinib was well tolerated and showed significant activity, allowing an OR of 54.5% (27% CR and 27% PR) and a duration of response that reached 12.3 months (Fowler N H, Blood 2012 120: 21 Abstract 156). In a phase 2 study in relapsed/refractory DLBCL, Ibrutinib was well tolerated, with OR of 21.7% (5% CR and 16.7% PR) (Wilson W H, Blood 2012 120:21 Abstract 686.). Finally, impressive results were obtained in a multicenter, phase 2 Study of Ibrutinib, in relapsed or refractory MCL with an OR of 66.1% (19.3% CR and 46.8% PR)(Wang, M, Blood 2012 120:21 Abstract 904).
From the previous discussion it becomes evident that there still is a non-satisfied need for clinically effective agents for the treatment of mature B cell neoplasms, more particularly for the treatment of CLL, MCL, FL and DLBCL and that targeting one or more of LYN, SYK, and BTK kinases with small molecular inhibitors seems to be a promising strategy in the treatment of these mature B cell neoplasms (CLL, MCL, FL and DLBCL).
The inventors have surprisingly found that 4-amino-6-(2,6-dichlorophenyl)-2-(phenylamino)-pyrido[2,3-d]pyrimidin-7(8H)-one derivatives of formula (I) are capable of inhibiting one or more of BCR-related kinases (LYN, SYK, and/or BTK) kinases, arresting the growth of NHL cell lines. In addition, these compounds show low toxicity values in vitro. This discovery makes these compounds promising candidates for the treatment of non-Hodgkin's lymphomas, in particular for the treatment of mature B cell neoplasm, more particularly for the treatment of CLL, MCL, FL and DLBCL. The inventors have also discovered a process for obtaining these 4-amino-6-(2,6-dichlorophenyl)-2-(phenylamino)-pyrido[2,3-d]pyrimidin-7(8H)-one derivatives.